diff --git a/include/mbedtls/ssl_internal.h b/include/mbedtls/ssl_internal.h
index 21f11ed..17bb631 100644
--- a/include/mbedtls/ssl_internal.h
+++ b/include/mbedtls/ssl_internal.h
@@ -467,6 +467,7 @@
 
     void (*update_checksum)(mbedtls_ssl_context *, const unsigned char *, size_t);
     void (*calc_verify)(const mbedtls_ssl_context *, unsigned char *, size_t *);
+    MBEDTLS_CHECK_RETURN_CRITICAL
     int (*calc_finished)(mbedtls_ssl_context *, unsigned char *, int);
     mbedtls_ssl_tls_prf_cb *tls_prf;